Increasingly, research is being focused on drug-eluting optical contact lenses as a means for effective delivery of various ophthalmic medications, such as antibiotics. These drug-eluting contact lenses may include one or more thin coatings of a given drug, for example. The primary focus of such research is achieving sustained, controlled delivery of a given drug at the normal physiological temperature, pH and salinity of the human eye.
In vitro testing methods such as dissolution testing are useful for simulating the conditions under which a substance such as a pharmaceutical formulation is released under controlled conditions into a physiological environment, such as a gastrointestinal or vascular environment. The release of a sample formulation into appropriate media such as by dissolution facilitates the acquisition of optical signals or other data from which concentration, release rate or other information can be derived for prediction of or correlation with actual in vivo conditions. Some techniques entail agitation of the sample in media such as by stirring, rotation, or reciprocation.
To ensure validation of the data generated from dissolution-related procedures, dissolution testing is often carried out according to guidelines approved or specified by certain entities such as the United States Pharmacopoeia (USP), in which case the testing must be conducted within various parametric ranges. The parameters may include dissolution media temperature, the amount of allowable evaporation-related loss, and the use, position and speed of agitation devices, sample retention and/or holding devices, and other instruments operating in the test vessel.
For example, Chapters 711 (Dissolution) and 724 (Extended Release) of the USP guidelines describe the use of several techniques for performing agitation in test vessels containing a dissolution medium that is usually temperature-regulated. One of these techniques involves the use of a reciprocating holder (Apparatus 7). In Apparatus 7, various types of sample holders are attached to shafts and vertically reciprocated in vessels at a prescribed dip rate for the testing of dosage forms such as tablets and transdermal patches. However, conventional testing methods are not specifically designed for holding, supporting and testing newer types of pharmaceutical delivery means such as contact lenses. Without an effective holding apparatus, a contact lens may become deformed during in vitro testing. As a result, the resolution of data such as release rate data acquired during testing may not be optimized since the surfaces of the deformed contact lens may not adequately contact the dissolution medium during reciprocation, for example.
In view of the foregoing, there is a need for providing apparatus and methods specifically designed for effectively holding contact lenses during in vitro testing. In particular, there is a need for providing a contact lens holder that aids in maintaining a form or shape of the contact lens that is suitable for testing. In addition, there is a need for providing a contact lens holder that facilitates the free interchange (i.e., the proper distribution) of dissolution media within the holder so as to provide sufficient contact with the drug-containing surfaces of the contact lens.